Strings fitted on the guitar from factory are fine (my last two guitar purchases came that way) but a guitar that's been in a shop is a different matter entirely.

In my opinion, the difference in tone and feel between 10 - 40s and 9 - 42s won't be massive. Slightly heavier on the high end (but gains slightly on sustain and/or slight decrease in high end, but guitar is fitted with a tone knob); lighter and brighter on the low end.

Without actually hearing or seeing the guitar, I can't really comment on the condition of the current strings, but I do know every guitar I've bought from a shop has needed restringing straight away.